As one of constant velocity joints used for a drive shaft, etc. of a vehicle, a tripod type of joint is known.
The tripod type constant velocity joint includes, as exemplarily shown in FIGS. 9 and 10, a tripod 4 constructed in a manner that three trunnions 3 each having a roller 2 protruding in the normal direction to the axis are provided on one shaft 1 of an input and an output shafts and, and an outer housing 6 disposed at an end of the other shaft 5. The outer housing 6 has, on its inner periphery, three axially extending slide grooves 6a corresponding to the tripod 4. The constant velocity joint is constructed so that the rollers 2 of the tripod 4 are fitted in the slide grooves 6a to be axially slidable, thereby simultaneously enabling angulation of both shafts 1, 5 and enabling torque to be transferred between them.
In such constant velocity joints, it is general that for the purpose of preventing the ingress of dust or extraneous matter inside the joint or of retaining the grease sealed therein, a joint boot 100 moderately susceptible of extension and contraction and flexural deformation and assuming a bellows shape is mounted in a manner covering the part of the shaft 1 on the tripod 4 side from the outer housing 6. The joint boot 100 is formed at its axial one end as a large-diameter attachment part 101, which is fitted to the outer periphery of the outer housing 6 and fixed by means of a damping member 7 such as ring-like band and at its other end as a small-diameter attachment part 102, which is fixed to the outer periphery of the shaft 1 on the tripod 4 side by means of a clamping member 8 such as a ring-like band, wherein the both parts 101, 102 are linked integrally by a bellows part 103.
As illustrated in FIG. 10, the outer housing 6 is provided on the outer periphery thereof with three recessed portions 6b circumferentially equidistantly disposed and corresponding to the arrangement of the slide grooves 6a on the inner periphery thereof, and accordingly, the outer peripheral configuration of the outer housing 6 is non-circular, assuming a circumferentially tongued and grooved form (salient and reentrant form). In order to enable the mounting on the non-circular outer housing 6 like this, there is known a so-called two-piece type joint boot constructed so that between the outer housing 6 and the large-diameter attachment part 101, a bushing 105 in a discrete body may be interposed (cf. Patent Reference 1). The bushing 105 assumes, on its outer peripheral surface, a circular form in cross-section and is provided, in its inner peripheral area, with a plurality of lobe portions 104 protruding radially inwardly in a circumferentially distributed manner so as to conform to the recessed portions 6b of the outer housing.
Patent Reference 1: U.S. Pat. No. 5,529,538